Biosynthesis and Release of Multiple Peptides by the Caudodorsal Cells of Lymnaea Stagnalis

Abstract

The peptidergic Caudodorsal Cells (CDC) of the freshwater snail Lvmnaea stagnalis control egg laying and egg-laying behaviour by releasing various peptides that act upon different targets (e.g., Roubos, 1984; Geraerts et al., 1987). Egg laying lasts about 2 hours and involves ovulation of up to 200 oocytes from the ovotestis, packaging of these cells by various types of female accessory sex gland into an egg mass, and oviposition. Overt egg-laying behaviour consists of a number of stereotyped behavioural acts (Goldschmeding et al., 1983). It begins with cessation of locomotion and posture changes. After about one hour the animal starts crawling about and cleans the substrate by rasping with its buccal mass before depositing the egg capsule. Actual oviposition takes 10–20 minutes depending on the size of the egg mass (Dogterom et al., 1983). Finally, the animal crawls back along the egg mass, touching it with the lip, before moving off. In this paper a brief survey will be given of the mechanisms by which CDC activity is controlled, of the way the CDC synthesize and release their peptides, and of the effects of the CDC peptides upon their targets. This may help to clarify how the CDC initiate an egg-laying behaviour that is coordinated with other important physiological processes such as feeding, locomotion and copulation (Fig. 1). Particular attention will be paid to structure-function relationships of the CDC-system.